From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH 03/17] xen: arm32: ensure cmpxchg has full barrier semantics Date: Thu, 20 Mar 2014 17:22:20 +0000 Message-ID: <532B23CC.4090204@linaro.org> References: <1395330336.3104.12.camel@kazak.uk.xensource.com> <1395330365-9901-3-git-send-email-ian.campbell@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1395330365-9901-3-git-send-email-ian.campbell@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: stefano.stabellini@eu.citrix.com, tim@xen.org, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org Hi Ian, On 03/20/2014 03:45 PM, Ian Campbell wrote: > Unrelated reads/writes should not pass the xchg. > > Provide cmpxchg_local for parity with arm64, although it appears to be unused. > It also helps make the reason for the separation of __cmpxchg_mb more > apparent. > > With this our cmpxchg is in sync with Linux v3.14-rc7. > > Signed-off-by: Ian Campbell > --- > We got our cmpxchg implementation from Linux which AFAICS has always had these > additional barriers. I don't recall us having decided that Xen barriers should > not have this property as well, and if we did we were remiss in not adding a > comment etc... If my memory is faulty then I am happy to replace thispatch > with one which adds a comment instead. I think the barrier is good for Xen. We may have some place where both of this macro are used as a "barrier". Acked-by: Julien Grall Regards, -- Julien Grall